TWI801460B - Heating, ventilating and air conditioning (hvac) system, control method for a vapor compression system, and related machine-readable media - Google Patents

Abstract

A heating, ventilating, and air conditioning (HVAC) system that includes a vapor compression system having a refrigerant, a compressor of the vapor compression system configured to circulate the refrigerant through the vapor compression system, an expansion device of the vapor compression system configured to adjust a flow of the refrigerant through the vapor compression system, and a controller configured to adjust a position of the expansion device based on a measured amount of superheat of the refrigerant entering the compressor, a measured discharge temperature of the refrigerant leaving the compressor, or a combination thereof, such that the measured amount of superheat of the refrigerant entering the compressor reaches a target amount of superheat, the measured discharge temperature of the refrigerant leaving the compressor reaches a target discharge temperature, or a combination thereof.

Description

Heating, ventilation and air conditioning (HVAC) systems, for vapor compression systems Control method and related machine-readable medium

The present disclosure relates generally to heating, ventilation and air conditioning systems. In particular, the present disclosure relates to systems and methods for controlling electronic expansion valves (EEVs) in vapor compression systems.

Heating, Ventilating and Air Conditioning (HVAC, referred to as "HVAC") systems are widely used. For example, residential, commercial and industrial systems are used to control the temperature and air in homes and buildings using fluids such as refrigerants. HVAC systems circulate a refrigerant through a closed loop between an evaporator and a condenser, where the refrigerant absorbs heat at the evaporator, and where the refrigerant releases heat at the condenser. For example, a refrigerant may absorb heat from a first fluid and transfer heat to a second fluid to ultimately cool the first fluid and/or heat the second fluid. While passing through the evaporator, the refrigerant evaporates into a vapor by absorbing heat from the first fluid. The compressor then compresses the vapor causing an increase in the pressure and/or temperature of the vapor for subsequent passage through the condenser Cooling the second fluid in the fluid transfers heat from the first fluid to the second fluid.

In some cases, the vapor is superheated at the inlet of the compressor to ensure that the refrigerant is in a vapor state before entering the compressor. To control the superheat of the refrigerant entering the compressor, existing systems include liquid injection means to cool the vapor within the compressor. For example, the liquid injection device injects liquid refrigerant droplets into the compressor or at the inlet of the compressor to adjust the superheat of the vapor entering the compressor and/or the temperature of the vapor exiting the compressor. Unfortunately, liquid injection devices include additional components (eg, tubes, pumps, nozzles, etc.) to inject liquid refrigerant into the compressor. Furthermore, injecting liquid refrigerant into the compressor may reduce the performance of the compressor, and thus the performance of the HVAC system.

In one embodiment, a heating, ventilation and air conditioning (HVAC) system includes: a vapor compression system having a refrigerant; a compressor of the vapor compression system configured to circulate the refrigerant through the vapor compression system; An expansion device of the vapor compression system, the expansion device configured to adjust the flow of refrigerant through the vapor compression system; and a controller configured to based on the measured superheat of the refrigerant entering the compressor amount, the measured discharge temperature of the refrigerant leaving the compressor, or a combination thereof to adjust the position of the expansion device so that the measured superheat of refrigerant entering the compressor reaches the target superheat, the measured The discharge temperature of the refrigerant of the compressor reaches the target discharge temperature or a combination thereof.

In another embodiment, one or more tangible, non-transitory machine-readable media include processor-executable instructions for: receiving a first feedback of temperature and pressure of refrigerant entering a compressor of a vapor compression system Indicating, using the temperature and pressure of the refrigerant entering the compressor of the vapor compression system to determine the measured superheat of the refrigerant entering the compressor of the vapor compression system, receiving the refrigerant leaving the compressor of the vapor compression system a second feedback indication of the discharge temperature of the compressor, and adjust the vapor compression system based on the measured superheat of the refrigerant entering the compressor, the measured discharge temperature of the refrigerant leaving the compressor, or a combination thereof The location of the expansion device so that refrigerant entering the compressor reaches a target superheat, refrigerant leaving the compressor reaches a target discharge temperature, or a combination thereof.

In another embodiment, a method includes receiving a first feedback indication of the temperature and pressure of refrigerant entering a compressor of a vapor compression system, using the temperature and pressure of refrigerant entering a compressor of a vapor compression system to determine a measured superheat of refrigerant entering the compressor of the vapor compression system, receiving a second feedback indication of a discharge temperature of refrigerant exiting the compressor of the vapor compression system, and based on the measured superheat of refrigerant entering the compressor The superheat of the refrigerant, the measured discharge temperature of the refrigerant leaving the compressor, or a combination thereof to adjust the position of the expansion device of the vapor compression system so that the refrigerant entering the compressor reaches a target superheat, leaves The compressor's refrigerant reaches the target discharge temperature, or a combination thereof.

10: Heating, ventilation, air conditioning and refrigeration (HVAC&R) systems

12: Buildings

14: Vapor Compression System

16: Boiler

18: Air return pipe

20: Air supply pipe

22: Air handler

24: pipeline

72: Vapor Compression System

73: Refrigerant circuit

74: Compressor

76: condenser

78: Expansion valve or expansion device

80: evaporator

82: Console

84: Analog-to-digital (A/D) converter

86: Microprocessor

88: Non-volatile memory

90:Interface board

92:Variable Speed Drive (VSD)

94: motor

96: ambient air

98: Supply air flow

100: control circuit

104: Controller

106: Processor

108: memory

110, 112, 114, 116, 118: sensors

120: Actuator

140: Flowchart

142, 144, 148, 150, 154: frame

146: The first control module

152: Second control module

1 is a schematic diagram of environmental control for building environmental management that may employ one or more HVAC units according to one aspect of the present disclosure; FIG. 2 is a schematic diagram of the HVAC unit of FIG. 3 is a schematic diagram of the vapor compression system of FIG. 2 according to one aspect of the present disclosure; and FIG. 4 is a schematic diagram of the vapor compression system of FIGS. 2 and 3 according to one aspect of the present disclosure. Block diagram of the process of adjusting the electronic expansion valve.

Embodiments of the present disclosure relate to heating, ventilation, and air conditioning (HVAC) systems that adjust the position of an expansion device (e.g., an electronic expansion valve (EEV)) to control the superheat (e.g., suction superheat) of refrigerant entering a compressor. ) and/or the temperature of the refrigerant discharged from the compressor (eg, discharge temperature). According to an embodiment of the present disclosure, the HVAC system includes one or more control devices configured to adjust the position of the expansion device to control suction superheat and/or discharge temperature. As discussed above, existing HVAC systems use liquid injection devices that inject droplets of liquid refrigerant into the compressor. Unfortunately, the additional components used by the liquid injection devices add to the cost of the HVAC system. Furthermore, the liquid injection device degrades the performance of the compressor due to the liquid refrigerant coming into contact with the moving parts of the compressor.

Therefore, adjusting the expansion device to control the compressor suction superheat and/or discharge temperature can eliminate the liquid injection device from the HVAC system and Improve compressor performance. In some embodiments, the expansion device is controlled using a first control module (e.g., a suction superheat module) under a first set of operating parameters of the HVAC system, and a second control module is used under a second set of operating parameters of the HVAC system. A control module (eg, a discharge temperature module) controls the expansion device. For example, during start-up conditions (e.g., when starting the compressor to run for a predetermined amount of time) and/or when the superheat of the refrigerant entering the compressor (e.g., as determined by the pressure and temperature of the refrigerant) exceeds a first threshold , the first control module can be used. Additionally, a second control module may be utilized when a temperature of refrigerant discharged from the compressor exceeds a second threshold. In certain embodiments, an HVAC system includes a first controller (eg, a first proportional-integral-derivative (PID) controller) and a second controller (eg, a second PID controller), the first controller including a second A control module, the second controller includes a second control module. In other embodiments, the HVAC system includes a single controller (eg, a PID controller) that includes both the first control module and the second control module. In any case, the expansion device is adjusted based on the amount of superheat of the refrigerant flowing into the compressor (eg, suction superheat) and the temperature of the refrigerant discharged from the compressor (eg, discharge temperature). In this way, the temperature of the refrigerant can be controlled without injecting liquid droplets into the compressor, thereby increasing the efficiency of the compressor and/or the HVAC system.

Turning now to the drawings, FIG. 1 is a perspective view of an embodiment of an environment for a Heating, Ventilating, Air Conditioning and Refrigeration (HVAC&R) system 10 in a building 12 in a typical commercial environment. . HVAC&R system 10 may include vapor compression system 14 that supplies refrigerated liquid that may be used to cool building 12 . HVAC&R system 10 may also include a boiler 16 that supplies warm liquid to heat building 12 and an air distribution system that circulates air through building 12 . The air distribution system may also include an air return duct 18 , an air supply duct 20 and/or an air handler 22 . In some embodiments, air handler 22 may include a heat exchanger connected to boiler 16 and vapor compression system 14 by conduit 24 . The heat exchanger in air handler 22 may receive heated liquid from boiler 16 or chilled liquid from vapor compression system 14 , depending on the mode of operation of HVAC&R system 10 . HVAC&R system 10 is shown with individual air handlers on each floor of building 12, but in other embodiments, HVAC&R system 10 may include air handlers 22 and/or other components that may be shared between floors .

FIG. 2 is an embodiment of a vapor compression system 72 that may be used in the HVAC unit 12 described above. A vapor compression system 72 may circulate refrigerant through a refrigerant circuit 73 beginning with a compressor 74 . The circuit may also include a condenser 76 , expansion valve(s) or device(s) 78 and an evaporator 80 . Vapor compression system 72 may further include console 82 having analog-to-digital (A/D) converter 84 , microprocessor 86 , non-volatile memory 88 and/or interface board 90 . Console 82 and its components may be used to make adjustments to the operation of vapor compression system 72 based on feedback from an operator, from sensors of vapor compression system 72 detecting operating conditions, and the like.

In some embodiments, vapor compression system 72 may utilize one or more of variable speed drive (VSD) 92 , motor 94 , compressor 74 , condenser 76 , expansion valve or device 78 , and/or evaporator 80 . A motor 94 may drive compressor 74 and may be powered by a variable speed drive (VSD) 92 . VSD92 from AC The power supply receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency and provides power to the motor 94 with variable voltage and frequency. In other embodiments, the motor 94 may be powered directly by an AC or direct current (DC) power source. Motor 94 may comprise any type of electric motor that may be powered by a VSD or directly from an AC or DC source, such as a switched reluctance motor, induction motor, electronically commutated permanent magnet motor, or other suitable motor.

Compressor 74 compresses the refrigerant vapor and delivers the vapor to condenser 76 through a discharge passage. In some embodiments, compressor 74 may be a centrifugal compressor. Refrigerant vapor delivered by compressor 74 to condenser 76 may transfer heat to a fluid passing through condenser 76 , such as ambient or ambient air 96 . Due to heat transfer with ambient air 96 , the refrigerant vapor may condense into a refrigerant liquid in condenser 76 . Liquid refrigerant from condenser 76 may flow through expansion device 78 to evaporator 80 .

The liquid refrigerant delivered to evaporator 80 may absorb heat from another air stream, such as supply air stream 98 provided to building 10 or dwelling 52 . For example, supply air stream 98 may include ambient or ambient air, return air from a building, or a combination of both. The liquid refrigerant in the evaporator 80 may undergo a phase change from liquid refrigerant to refrigerant vapor. In this manner, evaporator 38 may reduce the temperature of supply air stream 98 via heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator 80 and returns through the suction line to the compressor 74 to complete the cycle.

In some embodiments, vapor compression system 72 may further include a reheat coil in addition to evaporator 80 . For example, the reheat coil can be positioned at The evaporator is downstream relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is subcooled so that the supply air stream 98 is 98 to remove water.

It should be understood that any of the features described herein may be incorporated with the HVAC unit 12, the residential heating and cooling system 50, or other HVAC systems. Furthermore, while the features disclosed herein are described in the context of embodiments for direct heating and cooling of supply air streams provided to buildings or other loads, embodiments of the present disclosure may also be applied to other HVAC systems. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications.

As discussed above, in some embodiments, expansion device 78 is an electronic expansion valve (EEV), which may be adjusted to control the temperature of refrigerant entering and/or exiting compressor 74 . Existing systems use a liquid injection system to control the temperature of the refrigerant in the compressor 74 . Unfortunately, the liquid injection system can reduce the efficiency of the compressor 74 and/or the HVAC unit 12 . Accordingly, embodiments of the present disclosure relate to utilizing a first control module (eg, a suction superheat module) under a first set of operating parameters of the HVAC system and utilizing a second control module under a second set of operating parameters of the HVAC system The expansion device 78 is controlled (eg, a discharge temperature module). For example, the first control module may be utilized during start-up conditions (eg, when compressor 74 is started running for a predetermined amount of time) and/or when the temperature of refrigerant entering compressor 74 exceeds a first threshold. Additionally, a second control module may be utilized when the temperature of the refrigerant discharged from compressor 74 exceeds a second threshold.

FIG. 3 illustrates a control circuit 100 that may be used to control the operation of expansion device 78 in vapor compression system 72 as described in FIG. 2 . The expansion device 78 may be adjusted based on the amount of superheat of the refrigerant entering the compressor 74 (e.g., the suction of the compressor 74) and/or the temperature of the refrigerant exiting the compressor 74 (e.g., the discharge of the compressor 74). Location. That is, the control circuit 100 can adjust the position of the expansion device 78 to obtain a flow rate of refrigerant such that the superheat of the refrigerant at the outlet of the evaporator 80 and/or at the inlet of the compressor 74 reaches the target superheat. Additionally, the control circuit 100 may adjust the position of the expansion device 78 to achieve a flow rate of refrigerant that causes the temperature of the refrigerant discharged from the compressor 74 to reach the target discharge temperature. The control circuit 100 may include a controller 104, such as a microcontroller. Controller 104 may include a processor 106 operatively coupled to memory 108 to execute software, such as software for controlling the position of expansion device 78 . Furthermore, processor 106 may include multiple processors, one or more "general purpose" microprocessors, one or more special purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), or some combination thereof . For example, processor 106 may include one or more Reduced Instruction Set (RISC) processors, Advanced RISC Machine (ARM) processors, performance optimized with Enhanced RISC (PowerPC) processors, Field Programmable Gate Array (FPGA) ) integrated circuit, graphics processing unit (GPU) or any other suitable processing device.

Memory device 108 may include volatile memory such as random access memory (RAM), nonvolatile memory such as read only memory (ROM), flash memory, or any combination thereof. Memory 108 can store various information that can be used for many different purposes. For example, memory 108 may store processor-executable instructions instructions (eg, firmware or software) that cause processor 106 to execute instructions such as for controlling expansion device 78 .

Processor 106 may execute instructions that receive one or more signals from one or more sensors of vapor compression system 72 . For example, control circuitry 100 (eg, a control system) may include sensors 110 , 112 , 114 , 116 , and/or 118 positioned on or around various components of vapor compression system 72 . For example, the control circuit 100 may include a temperature sensor 110 and a pressure sensor 112 positioned at the outlet of the evaporator 80 . The temperature sensor 110 may send a signal to the controller 104 indicating the temperature of the refrigerant as it exits the evaporator 80 . Similarly, pressure sensor 112 may send a signal to controller 104 indicating the pressure of the refrigerant as it exits evaporator 80 . Processor 106 may receive respective signals from temperature sensor 110 and pressure sensor 112 and determine the degree of superheat of the refrigerant as it exits evaporator 80 (and/or enters compressor 74 ), which is indicative of the relative The heat in the refrigerant at the refrigerant saturation point. For example, processor 106 may determine superheat by using a look-up table stored in memory 108 that defines the relationship between superheat and refrigerant at the outlet of evaporator 80 (and/or at the inlet of compressor 74). The relationship between temperature and pressure. The lookup table may be based on the physical characteristics of the refrigerant (eg, saturation point, quantity, etc.).

Additionally, the control circuit 100 may include a temperature sensor 114 (eg, a second temperature sensor) that monitors the temperature of the refrigerant discharged from the compressor 74 . As such, processor 106 may determine the discharge temperature of the refrigerant from compressor 74 and compare the discharge temperature to a threshold temperature, a predetermined temperature range, or a combination thereof. Additionally or alternatively, the control circuit 100 may include a temperature sense sensor 116 (eg, a third temperature sensor) that monitors the temperature of the motor 94 configured to drive the compressor 74 . As such, processor 106 may determine the motor temperature and compare the motor temperature to a threshold motor temperature, a predetermined motor temperature range, or a combination thereof. In some implementations, an ambient temperature sensor 118 may be positioned near the vapor compression system 72 to detect the temperature of the surrounding air. While sensors 110 , 112 , 114 , 116 , and/or 118 are described in detail, any suitable sensor that detects operating conditions of vapor compression system 72 may be used.

Processor 106 may receive one or more signals indicative of operating conditions (eg, temperature, pressure, vibration, etc.) of vapor compression system 72 . Processor 106 may then be configured to activate and/or use control modules of processor 106 based on one or more signals indicative of the operating condition of vapor compression system 72 . For example, processor 106 may compare a predetermined amount of superheat of refrigerant leaving evaporator 80 (and/or entering compressor 74) (e.g., a target or setpoint superheat) with a measured amount of refrigerant leaving evaporator 80 (and/or entering compressor 74). /or the superheat of the refrigerant entering the compressor (74) is compared. Additionally, processor 106 may compare a predetermined discharge temperature of refrigerant exiting compressor 74 (eg, a target discharge temperature or a setpoint discharge temperature) to a measured discharge temperature of refrigerant exiting compressor 74 . Processor 106 may then determine an appropriate control module to use and/or enable based on the comparison performed by processor 106 .

When the processor 106 is operating under the first control module (eg, suction superheat control), the processor 106 bases the target superheat on the refrigerant leaving the evaporator 80 and/or entering the compressor 74 and the measured superheat The difference between to adjust the expansion device 78. For example, if the target superheat is 10 degrees Fahrenheit (°F) above the refrigerant saturation point and the measured superheat (eg, based on the temperature and pressure of the refrigerant exiting the evaporator 80 and/or entering the compressor 74) is higher than the saturation point 5°F, the processor 106 may send a signal to the actuator 120 (eg, a motor or stepper motor) of the expansion device 78 to adjust the position of the expansion device 78 . In this manner, the position of the expansion device 78 can be adjusted to reduce the flow rate of the refrigerant directed to the evaporator 80, thereby increasing the superheat of the refrigerant to eventually achieve the target superheat of 10°F.

Additionally, when the processor 106 is operating under a second control module (eg, discharge temperature control), the processor 106 adjusts the temperature based on the difference between the target discharge temperature of the refrigerant exiting the compressor 74 and the measured discharge temperature. Expansion device 78. For example, processor 106 adjusts the position of expansion device 78 via actuator 120 when the target discharge temperature is 175°F and the measured discharge temperature is 160°F. As such, the position of the expansion device 78 is adjusted to decrease the flow of refrigerant through the compressor 74 and to increase the temperature of the refrigerant discharged from the compressor 74 . Further, in some embodiments, in addition to or instead of adjusting the position of the expansion device 78 based on the discharge temperature of the refrigerant, the processor 106 may base the temperature on the motor 94 driving the compressor 74 (eg, as determined by the sensor 116 ). measurement) to adjust the position of the expansion device 78.

Controller 104 may include one or more proportional-integral-derivative (PID) controllers, fuzzy logic controllers, or any other suitable controller 104 to implement a control module that adjusts expansion device 78 to achieve a target superheat amount, target discharge temperature, and/or target motor temperature. Based on operating parameters measured from one or more sensors 110, 112, 114, 116, and/or 118, controller 104 Switching between different control modules (eg, suction superheat control module, discharge temperature control module and/or motor temperature control module).

For example, FIG. 4 is a block diagram of a flowchart 140 illustrating the logic executed by the controller 104 to operate and switch between control modules. For example, at block 142 the compressor 74 is disabled (eg, powered off or not enabled). As such, the vapor compression system 72 may not circulate the refrigerant. Accordingly, expansion device 78 is not adjusted to control the flow rate of refrigerant to evaporator 80 because the refrigerant is not circulated through vapor compression system 72 via compressor 74 .

At block 144 , a start-up sequence for the compressor 74 may be initiated with the controller 104 operating under the first control module 146 (eg, suction superheat control). For example, the first control module 146 may include an activation sequence whereby the controller 104 sends a signal to the expansion device 78 to adjust the position of the expansion device 78 to the activated position for a predetermined amount of time (e.g., 1 second, 2 seconds, 3 seconds , 4 seconds, 5 seconds or more than 5 seconds). For example, when expansion device 78 is in the activated position, expansion device 78 may circulate a relatively high flow rate of refrigerant through vapor compression system 72 such that vapor compression system 72 may quickly reach steady state operation.

At block 148 , the controller 104 may experience the suction superheat control ramp of the first control module 146 once the predetermined amount of time has elapsed from the activated position of the expansion device 78 . For example, once vapor compression system 72 has substantially reached steady state operation, controller 104 adjusts expansion device 78 such that the superheat of refrigerant exiting evaporator 80 and entering compressor 74 (e.g., the suction of compressor 74) to reach the target superheat. As such, controller 104 sends a second signal to expansion device 78 to adjust expansion based on feedback received from sensors 110 , 112 , 114 , 116 , and/or 118 The location of the device 78. In some embodiments, the controller 104 is configured to adjust the expansion device 78 to a threshold position (eg, a predetermined position that circulates a minimum amount of refrigerant through the vapor compression system 72 ) or a commanded position based on a target superheat. For example, the commanded position is determined by the controller 104 as the position of the expansion device 78 such that the superheat of the refrigerant exiting the evaporator 80 and entering the compressor 74 reaches a target degree of superheat. The controller 104 compares the threshold position to the commanded position and selects the position corresponding to the higher flow rate of refrigerant through the vapor compression system 72 . In other words, controller 104 may correlate the position of expansion device 78 with a value proportional to the flow rate of refrigerant through vapor compression system 72 . As such, controller 104 selects a position (eg, a threshold position or a commanded position) that includes a higher value without blocking circulation of refrigerant through vapor compression system 72 .

Additionally, at block 150 , the controller 104 may operate under suction superheat control of the first control module 146 once the measured refrigerant superheat reaches the target superheat. In some embodiments, the suction superheat control may be similar to the suction superheat control ramp, with minor adjustments to the position of the expansion device 78 as indicated at block 148 (e.g., the suction superheat control ramp may adjust the position of the expansion device 78 large adjustments in position to quickly reach target superheat). In other words, the suction superheat control of block 150 is used to maintain the measured superheat of the refrigerant leaving the evaporator 80 and entering the compressor 74 at the target superheat. Accordingly, relatively minor adjustments to the expansion device 78 are made during the suction superheat control of block 150 .

During suction superheat control at block 150 , controller 104 sends a third signal to expansion device 78 to adjust the position of expansion device 78 based on feedback received from sensors 110 , 112 , 114 , 116 , and/or 118 . Controller 104 is configured to The expansion device 78 is adjusted to a threshold position (eg, a predetermined position that circulates a minimum amount of refrigerant through the vapor compression system 72 ) or a commanded position based on a target degree of superheat. In some embodiments, the threshold position of the suction superheat control of block 150 is the same as the threshold position of the suction superheat control ramp of block 148 . However, in other implementations, the threshold location for the suction superheat control of frame 150 is different than the threshold location for the suction superheat control ramp of frame 148 . In any event, the commanded position is determined by the controller 104 as the position of the expansion device 78 such that the superheat of the refrigerant exiting the evaporator 80 and entering the compressor 74 reaches the target degree of superheat. The controller 104 compares the threshold position to the commanded position and selects the higher value corresponding to the higher flow rate of refrigerant through the vapor compression system 72 (or the higher value corresponding to the flow rate of refrigerant through the vapor compression system 72 ). Positioned so that circulation of the refrigerant through the vapor compression system 72 is not blocked.

As described above, controller 104 is configured to control the temperature of first control module 146 and second control module 152 based on the operating parameters of vapor compression system 72 monitored by sensors 110 , 112 , 114 , 116 , and/or 118 . switch between. For example, controller 104 may be configured to switch from first control module 146 (eg, suction superheat control) to a second control module 146 based at least on the discharge temperature of refrigerant exiting compressor 74 (eg, as measured by sensor 114 ). Control module 152 (eg, discharge temperature control). Controller 104 may compare the measured discharge temperature from sensor 114 to one or more discharge temperature thresholds stored in memory 108 of controller 104 . In some embodiments, when the measured discharge temperature exceeds a first discharge temperature threshold for a predetermined amount of time (e.g., 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, or more than 5 seconds), the controller 104 starts from The first control module 146 switches to the second control module 152 . also, The controller may be configured to switch from the first control module 146 to the second control module 152 immediately when the measured discharge temperature exceeds a second discharge temperature threshold, wherein the second discharge temperature threshold is one greater than the first discharge temperature threshold Offset. In some embodiments, the offset between the first discharge temperature threshold and the second discharge temperature threshold is between 5°F and 50°F, between 7°F and 25°F, or between 8°F and 15°F between.

When the controller 104 is operating under the second control module 152 , the controller 104 adjusts the position of the expansion device 78 based on the measured discharge temperature to achieve the target discharge temperature, as indicated at block 154 . For example, when the measured discharge temperature is below the target discharge temperature, controller 104 sends a signal to adjust the position of expansion device 78 to reduce the flow of refrigerant through vapor compression system 72 (e.g., to reduce the flow of refrigerant through evaporator 80). The flow rate of the refrigerant increases the temperature of the refrigerant discharged from the compressor 74). Similarly, when the measured discharge temperature exceeds the target discharge temperature, controller 104 sends a signal to adjust the position of expansion device 78 to increase the flow of refrigerant through vapor compression system 72 (e.g., increase the flow of refrigerant through evaporator 80 The flow rate of the refrigerant reduces the temperature of the refrigerant discharged from the compressor 74). As noted above, in other embodiments, the second control module 152 may adjust the position of the expansion device 78 based on the temperature of the motor 94 in addition to or instead of the discharge temperature of the refrigerant from the compressor 74 .

As noted above, the signal sent from controller 104 may include a position of expansion device 78 selected from a threshold position (e.g., a predetermined position at which the least amount of refrigerant is circulated through vapor compression system 72) and a position based on measured Command position for discharge temperature. In some embodiments, the threshold position of the discharge temperature control of box 154 is consistent with the suction superheat ramp control of box 148 and/or the suction superheat control of box 150. The threshold position of the control is the same or different. The commanded position is determined by the controller 104 as the position of the expansion device 78 such that the discharge temperature of the refrigerant exiting the compressor 74 reaches the target discharge temperature. The controller 104 compares the threshold position to the commanded position and selects the position corresponding to the higher flow rate of refrigerant through the vapor compression system 72 . In other words, controller 104 may correlate the position of expansion device 78 with a value proportional to the flow rate of refrigerant through vapor compression system 72 . As such, controller 104 selects a position (eg, a threshold position or a commanded position) that includes a higher value without blocking circulation of refrigerant through vapor compression system 72 .

In some implementations, the second control module 152 overrides the first control module 146 (eg, suction superheat override). For example, in some cases, the expansion device 78 is adjusted to achieve a target discharge temperature such that the suction superheat is reduced below a predetermined amount. In this way, although the superheat degree of the refrigerant is lower than the target superheat degree, the controller 104 still overrides the first control module 146 .

Additionally, controller 104 receives feedback from sensors 110 and 112 that indicate the temperature and pressure of the refrigerant exiting evaporator 80 (and/or entering compressor 74 ). As noted above, the temperature and pressure of the refrigerant exiting evaporator 80 (and/and entering compressor 74 ) may be used to determine the superheat of the refrigerant. When the measured amount of superheat (e.g., determined from feedback from sensors 110 and 112) exceeds a first overheat threshold for a predetermined amount of time (e.g., 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, or more than 5 seconds), the controller 104 may switch from the second control module 152 to the first control module 146 (eg, from block 154 to block 150). Additionally, the controller 104 may immediately switch from the second control module 152 to the first control module 146 when the measured superheat exceeds a second overheat threshold, wherein the second overheat threshold is greater than the first overheat threshold. The controller 104 may then operate under the first control module 146 and adjust the position of the expansion device 78 based on the measured superheat of the refrigerant exiting the evaporator 80 (and/or entering the compressor 74).

As noted above, embodiments of the present disclosure may provide one or more technical effects for operation of an HVAC system to increase compressor efficiency. For example, embodiments of the present disclosure relate to controlling the position of the electronic expansion valve based on the amount of superheat of the refrigerant exiting the evaporator and/or the refrigerant entering the compressor and the discharge temperature of the refrigerant exiting the compressor. Control of the electronic expansion valve enables regulation of the operating temperature of the refrigerant passing through the compressor without the use of a liquid injection system that directs liquid refrigerant droplets into the compressor. Eliminating and/or reducing liquid droplets within the compressor increases the efficiency of the compressor and thus improves the operation of the HVAC system. The technical effects and technical problems in this specification are illustrative rather than restrictive. It should be noted that the implementations described in this specification may have other technical effects and may solve other technical problems.

While only certain features and implementations have been shown and described, many modifications and changes (e.g., Variations in size, dimensions, structure, shape and proportions of various elements, parameter values (eg, temperature, pressure, etc.), mounting arrangements, use of materials, colors, orientations, etc.). The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure. Additionally, in order to provide a brief description of the exemplary embodiments, the All features of the actual implementation (i.e., those features that are not relevant to the currently expected best mode or those features that are not relevant to enabling). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, a number of implementation-specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, production, and fabrication without undue experimentation for those of ordinary skill having the benefit of this disclosure.

140: Flowchart

142, 144, 148, 150, 154: box

146: The first control module

152: Second control module

Claims (11)

A heating, ventilation and air conditioning (HVAC) system comprising: a vapor compression system including a refrigerant; a compressor of the vapor compression system configured to circulate the refrigerant through the vapor compression system; an expansion device of a vapor compression system, the expansion device configured to adjust the flow of refrigerant through the vapor compression system; and a controller configured to operate in accordance with a first control module to based on the measured the amount of superheat of refrigerant entering the compressor to adjust the position of the expansion device to achieve a target superheat, and is configured to operate in accordance with a second control module to operate based on the measured adjusting the position of the expansion device to achieve a target discharge temperature, wherein the controller is configured to adjust the position of the expansion device when the measured discharge temperature of the refrigerant leaving the compressor exceeds a first switching from the first control module to the second discharge temperature threshold when the discharge temperature threshold reaches a predetermined amount of time, or when the measured discharge temperature of the refrigerant leaving the compressor exceeds a second discharge temperature threshold A control module, wherein the second discharge temperature threshold is greater than the first discharge temperature threshold. The HVAC system of claim 1, wherein said controller is configured when said measured superheat of refrigerant entering said compressor exceeds a first superheat threshold for said predetermined amount of time, or When the measured superheat of the refrigerant entering the compressor exceeds a second superheat threshold, switching from the second control module to the first control module, wherein the second superheat threshold is greater than the first overheating threshold. The HVAC system of claim 1 wherein said controller is configured to issue a position to said expansion device when operating under said first control module and wherein the signal includes a threshold position of the expansion device or a commanded position of the expansion device based on the measured superheat of refrigerant entering the compressor such that across the The one with the larger refrigerant flow rate of the expansion device. The HVAC system of claim 1, wherein said controller is configured to signal an adjustment to the position of said expansion device when operating under said second control module, and wherein said signal comprises said The threshold position of the expansion device or the commanded position of the expansion device based on the measured discharge temperature of the refrigerant leaving the compressor, whichever results in a greater flow of refrigerant through the expansion device By. The HVAC system of claim 1, wherein said controller is configured to operate under said first control module during startup of said compressor. The HVAC system as claimed in claim 1, wherein the expansion device is an electronic expansion valve. The HVAC system of claim 1, comprising a motor configured to drive the compressor, wherein the controller is configured to adjust the position of the expansion device based on a measured motor temperature of the motor to Target motor temperature reached. A tangible, non-transitory machine-readable medium comprising processor-executable instructions for: receiving a first feedback indication of temperature and pressure of refrigerant entering a compressor of a vapor compression system; utilizing the temperature and pressure of the refrigerant in the compressor to determine the measured superheat of the refrigerant entering the compressor of the vapor compression system; receiving a second feedback indication of a discharge temperature of refrigerant exiting a compressor of the vapor compression system; and adjusting a position of an expansion device of the vapor compression system with the first control module or the second module, wherein the The first control module is configured to adjust the expansion device to achieve a target superheat based on the measured superheat of refrigerant entering the compressor, and the second control module is configured to adjust the expansion device based on the discharge temperature of the refrigerant leaving the compressor to adjust the expansion device to achieve a target discharge temperature; and when the discharge temperature of the refrigerant leaving the compressor exceeds a first discharge temperature threshold for a predetermined time amount, or when the discharge temperature of the refrigerant leaving the compressor exceeds a second discharge temperature threshold, switching from the first control module to the second control module, wherein the second The discharge temperature threshold is greater than the first discharge temperature threshold. The tangible, non-transitory machine-readable medium of claim 8, wherein the processor-executable instructions are configured to, when the measured superheat of refrigerant entering the compressor exceeds a first superheat threshold for switching from the second control module to the first control module when the predetermined amount of time, or when the measured superheat of the refrigerant entering the compressor exceeds a second superheat threshold , wherein the second overheating threshold is greater than the first overheating threshold. A control method for a vapor compression system comprising: receiving a first feedback indication of the temperature and pressure of refrigerant entering a compressor of said vapor compression system; utilizing the temperature of refrigerant entering a compressor of said vapor compression system and pressure to determine a measured superheat of refrigerant entering a compressor of said vapor compression system; receiving a second feedback indication of a discharge temperature of refrigerant exiting a compressor of the vapor compression system; and adjusting a position of an expansion device of the vapor compression system with the first control module or the second module, wherein the The first control module is configured to adjust the expansion device to achieve a target superheat based on the measured superheat of refrigerant entering the compressor, and the second control module is configured to adjust the expansion device based on the discharge temperature of the refrigerant leaving the compressor to adjust the expansion device to achieve a target discharge temperature; and when the discharge temperature of the refrigerant leaving the compressor exceeds a first discharge temperature threshold for a predetermined time amount, or when the discharge temperature of the refrigerant leaving the compressor exceeds a second discharge temperature threshold, switching from the first control module to the second control module, wherein the second The discharge temperature threshold is greater than the first discharge temperature threshold. The control method as recited in claim 10, comprising when said measured superheat of refrigerant entering said compressor exceeds a first superheat threshold for said predetermined amount of time, or when said measured refrigerant entering Switching from the second control module to the first control module when the superheat of the refrigerant in the compressor exceeds a second overheat threshold, wherein the second overheat threshold is greater than the first overheat threshold.

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